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Saturday, 18 May 2013

Land abandonment and the decline of the Yellow-bellied toad in Liguria, northern Italy

Across Europe, centuries of interactions
between low-intensity human activities, such as extensive small-scale farming,
and the surrounding environment have created what we now call “cultural
landscapes”, which provide important ecosystem services and often support a
rich biodiversity. However, since the second half of the 20thcentury several countries have witnessed large-scale social changes that have
led to modifications in these landscape dynamics. There is growing evidence
that this can also entail an impact to biodiversity, as the intermediate
disturbance that can benefit species is lost or replaced by more disruptive activities
(such as intensive vs. extensive farming: MacDonald 2000).These same dynamics may be a leading factor
in the disappearance of the yellow-bellied toad Bombina pachypus from peninsular Italy (Figure 1). The species has declined in
the last thirty years and is now listed as Endangered by the IUCN. However, the
causes of this decline are still unclear: in Liguria, northern Italy, habitat
loss is believed to be the main driver, with recent systematic monitoring for
the amphibian fungal disease chytridiomycosis failing to detect signs of this
devastating pathogen (Canessa et al, in
press).

In a recent study, we monitored sites across
the region that were known to host the species until 2005: these were a
combination of artificial sites (stone washtubs) and natural sites (small mountain
creeks). We found that only five years later, in 2010, more than 50% of the
populations had disappeared. When we searched for common traits among the sites
where local extinctions had occurred, we found they had high densities of
predators (dragonflies and newts), low insulation and dense vegetation. These in
turn were linked to disturbance, with more frequent flooding and desiccation cycles
beneficial in removing vegetation and predators and favouring tadpole survival.
In natural sites, flooding and desiccation
are natural processes, and where they continue the species still occurs in
relatively large numbers. On the other hand, in artificial sites disturbance is
provided by traditional management (cleaning and dredging) (Figure 2): after land parcels
or traditional practices are abandoned, sites degrade rapidly and become
unsuitable. Significantly, in our study all artificial sites that had been
abandoned by farmers immediately prior to or after 2005 did not host toad
populations when we re-sampled them. Artificial sites that were still maintained
(and therefore disturbed) were still occupied by the species.

Figure
2. The transition between a maintained artificial water body (left) and an abandoned one unsuitable
for yellow-bellied toads (right) can
occur within a few years (photos: S. Canessa)

This preference for disturbed sites matches
observations for other yellow-bellied toads in Europe (Warren and Büttner, 2008),
provides significant information for local conservation actions, and suggests
the need to link ecological and socio-economic objectives: for example, in
Liguria current efforts for the conservation of the yellow-bellied
toad focus on the integration of traditional practices and biodiversity
conservation in new forms of human activities, such as sustainable farming or
eco-tourism. On the basis of this study, the Regional Park of Monte Marcello –
Magra is coordinating a project, funded by the regional administration of
Liguria, which includes the recovery of several semi-natural sites and the
creation of new artificial sites that can be used by local farmers whilst
providing suitable habitat for the species.The conservation of culture and
biodiversity needs is deeply connected in many parts of Europe: this requires an
approach that is somewhat contradictive of the usual point of view of human
activities as inherently negative. However, where large scale processes such as
land abandonment are involved, they may be difficult to reverse by conservation
funding alone. However, where traditional practices are still widespread, it is
imperative that social and environmental planning should take into account the
impacts on biodiversity that the abandonment of such practices may entail.Canessa, S.a, Oneto, F.b,
Ottonello, D.b, Arillo, A.b and Salvidio, S.b
(2013). Land abandonment may reduce disturbance and affect the breeding sites
of an endangered amphibian in northern Italy. Oryx, 47(2): 280-287a ARC
Centre of Excellence for Environmental Decisions, School of Botany, University
of Melbourne, 3010 Victoria, Australia b
Dipartimento di Scienze della Terra, dell’Ambiente e della Vita, University of
Genoa, Genoa, ItalyCited
referencesCanessa, S., Martel, A. and Pasmans, F. (in press). No detection of chytrid in
first systematic screening of Bombina
variegata pachypus (Anura: Bombinatoridae) in Liguria, northern Italy. Acta Herpetologica.MacDonald, D., Crabtree, J.R., Wiesinger,
G., Dax, T., Stamou, N., Fleury, P., Gutierrez-Lazpita, J. and Gibon, A. (2000)
Agricultural abandonment in mountain areas of Europe: environmental
consequences and policy response. Journal
of Environmental Management, 59: 47-69.Warren, S.D. , Büttner, R. (2008):
Relationship of endangered amphibians to landscape disturbance. The Journal of Wildlife Management 72:
738-744.Contributed by Stefano Canessa, ARC Centre
of Excellence for Environmental Decisions, School of Botany, University of
Melbourne, 3010 Victoria, AustraliaE-mail: canessas@unimelb.edu.auPersonal blog: http://www.canessas.wordpress.com

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